Packet telephony involves the use of a packet network, such as the Internet or an "intranet" (modeled in functionality based upon the Internet and used by a companies locally or internally) for telecommunicating voice, pictures, moving images and multimedia (e.g., voice and pictures) content. Instead of a pair of telephones connected by switched telephone lines, however, packet telephony typically involves the use of a "packet phone" or "Internet phone" at one or both ends of the telephony link, with the information transferred over a packet network using packet switching techniques. A "packet phone" or "Internet phone" typically includes a personal computer (PC) running application software for implementing packetized transmission of audio signals over a packet network (such as the Internet); in addition, the PC-based configuration of a packet or Internet phone typically includes additional hardware devices, such as a microphone, speakers and a sound card, which are plugged or incorporated into the PC.
Furthermore, packet telephony includes a broad spectrum of media or signal types. Whereas the plain old telephone service (POTS) networks have primarily been concerned with sound (and, over the last several years, data) transmission, packet telephony includes--in addition to voice/data--pictures or images, moving pictures, and multimedia content. Incorporating the capability of handling multimedia content increases the complexity of end devices for packet telephony.
Regular telephone devices used with POTS networks are simple, highly reliable devices. Users typically do not tamper with them during the life of the telephone. The reliability of regular telephones is limited only by the manufacturing process.
In contrast, devices used for packet telephony, such as PC-based packet phones, are dynamically-configured machines, with operation controlled (and resources allocated) in part by one or more executable software programs, and much more complex in their operation with higher hardware failure rates. In addition, PCs used for packet phones are not dedicated telephony devices, so the reliability of a PC-based packet phone may well be limited by other applications that may run on the PC; for example, a crash caused by any other application that renders the PC inoperative (i.e., the computer is "hung") would also render the PC-based packet phone inoperative. While some PC products contain as a feature the ability of a PC to wake up, receive a phone call and go back to sleep, such a feature requires an operational PC; if the PC has crashed, the "wake up" phone call feature will be rendered inoperable.
While consumers have become accustomed to failures in computers and PC equipment, they have not been accustomed to failures in their telephones; in fact, consumers have become accustomed to a highly reliable, ubiquitous telephone service that has been available for years through POTS. The shift in telephony from POTS networks and telephones to packet networks and PC-based packet telephony devices, thus, brings about the need for increased reliability in packet telephony devices.
What is desired is a practical way to improve the reliability of packet telephony devices, such as a PC-based packet phone, so that the reliability of network communications through packet telephony approaches the reliability of POTS telephony.